HSC Survey Results

Scots Bay Survey # 10 Results from 08/09/2024

Survey Details

3 commercial purse seiners conducted this fishing survey on 08/09/2024 starting at 20:00:00, which was 4.03 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 13,418mt, and with turnover applied 12,121mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
FM T01 2024-09-08 20:36:24 2024-09-08 23:24:17 -65.231 45.089 -64.774 45.244 SB 40.67 7.85
FM T02 2024-09-08 23:58:04 2024-09-09 02:19:14 -64.836 45.307 -65.236 45.166 SB 36.17 8.30
LB T01 2024-09-08 19:24:29 2024-09-08 22:47:59 -65.231 45.037 -64.685 45.215 SB 48.01 7.64
LB T02 2024-09-08 23:25:30 2024-09-09 02:46:19 -64.768 45.274 -65.233 45.115 SB 41.41 6.68
LM T01 2024-09-08 19:28:34 2024-09-08 22:24:13 -65.243 45.063 -64.716 45.234 SB 45.83 8.45
LM T02 2024-09-08 22:55:55 2024-09-09 01:28:14 -64.796 45.292 -65.237 45.137 SB 39.18 8.33

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
FM T01 -35.5 -47.973 0.057
FM T02 -35.5 -51.086 0.028
LB T02 -35.5 -52.592 0.020
LM T02 -35.5 -54.641 0.012
LB T01 -35.5 -55.853 0.009
LM T01 -35.5 -56.805 0.007
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 627.9545 -52.2023 0.0221 13,418.44 100 100 4,736.68 35.3

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by FM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by FM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,745 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,283 17,575 17,387 16,022
Scots Bay 6 2024-07-15 4,539 3,560 2023-07-30 4,550 1,904 3,474 1,093
Scots Bay 7 2024-07-29 32,655 32,016 2023-08-13 4,299 3,616 2,777 2,247
Scots Bay 8 2024-08-11 15,213 10,296 2023-08-27 2,897 2,300 1,612 1,224
Scots Bay 9 2024-08-25 9,206 6,810 2023-09-10 3,054 2,916 3,219 0
Scots Bay 10 2024-09-08 13,418 12,121 2023-09-24 3,420 2,997 2,318 0
Scots Bay 11 NA NA NA 2023-10-09 3,388 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,538 204,189 218,266 177,329
2024 Scots Bay 317,938 275,644 NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number SB2024-17 SB2024-18
Ground SB SB
Date 08/09/2024 08/09/2024
Wind Direction (km/h) SW SW
Swell (m) 0.5 0.5
Air Temp (c) 15 15
Tow Details
Tow Start 18:43:00 19:06:00
Tow End 18:53:00 19:16:00
Start Lat 45.04100 45.05217
End Lat 45.05233 45.05267
Start Lon -65.24133 -65.21967
End Lon -65.2375 -65.7060
Avg Tow Depth (m) 12.257411 6.073662
Speed 5.0 4.2
Heading 1 77
Tide Direction with against
Other Data Collection
Flow Start 599420 665543
Flow End 665543 725094
No. Revolutions 66123 59551
Distance (m) 1776.923 1600.314
Volume 5582.205 5027.387
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-17, which was with the tide and had an average depth of 12.2574109m. The second tow is SB2024-18, which was against the tide and had an average depth of 6.0736616m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

The vessels performed well and the average vessel speed was 7.88 which is below the requirements of 8 knots.

The speed for each transect are rudimentary and are calculated based on distance. If a significant amount of distance is cut, the speed will appear slower.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.